Flow patterns and shear stress investigation and in vitro studies of blood pump

The long-term clinical use of blood pumps is dependent on the bio-compatibility. Blood trauma especially hemolysis is closely related to the flow fields in the pumps according to the homodynamic. Computational fluid dynamics technique has been used to visualize the flow patterns and distribution of shear stress in two pumps with different impeller designs and to evaluate the hemolysis level. After analysis of the flow patterns, it is found that the streamlined design developed by the authors has irregular flow patterns while disorder flows such as vortex, flow separation and back flow appeared in the pump with straight vanes in the design point (4L/min, 100mmHg). The distributions of wall shear in two pumps present that the streamlined pump has the lower maximum shear stress (186Pa) in the volute and no nodes by which the shear beyond the critical value (150Pa) leading to hemolysis, while the pump with straight vanes has the maximum shear of 280Pa and the nodes by which the shear beyond the critical value are as high as 74. It can be conclude that the in the same boundary conditions, streamlined pump has better bio-compatibility. Hemolysis tests were also made to validate the numerical results based on the circulatory model. The index of hemolysis of the the streamlined (0.03) was less than that of the Bio-pump with straight vanes (0.065).